1. Field of the Invention
The present invention relates to driving control for a solid state image pickup device.
2. Related Background Art
Conventionally there is known a method for driving a solid state image pickup device as shown in FIG. 1, in which there are shown an image sensor chip 1, a drive timing control device 2 such as a microcomputer (hereinafter called microcomputer) for controlling the image sensor chip 1 by outputting driving pulses therefore, drive mode control wirings 3, drive pulse wirings 5, a reference clock wiring 6, a drive pulse generation circuit 21 provided in the image sensor chip 1, and an image pickup unit/peripheral circuit 22 including plural photoelectric converting elements etc. and a peripheral circuit including horizontal and vertical scanning circuits.
FIG. 2 shows another conventional configuration, wherein shown are an image sensor chip 1 including the image pickup unit/peripheral circuit 22 shown in FIG. 1, a drive pulse generation circuit 4, and drive pulse wirings 5. The drive pulse generation circuit 4 is not integrated in an image sensor chip. In FIG. 2, the microcomputer 2, the drive mode control wirings 3, and the reference clock wiring 6 are the same as those in FIG. 1.
In the configuration shown in FIG. 1, the image sensor for outputting the image signal is operated by driving the image pickup unit and peripheral circuit 22 either directly by the drive mode control wirings 3 and the reference clock wiring 6 or by drive pulses generated in a circuit in the image sensor chip based on the drive mode control wirings 3 and the reference clock wiring 6. The configuration shown in FIG. 2 is employed in case requiring drive pulses of a strong driving force, wherein the required drive pulses are generated by the chip of the drive pulse generation circuit 4, based on the drive mode control wirings 3 and the reference clock wiring 6.
In either case, the operation mode of the image sensor chip 1 and the timing thereof are determined by the drive timing controlling device 2 such as the microcomputer, and the microcomputer 2 has to be operated in order to drive the image sensor chip 1.
However such conventional operation of the image sensor chip solely by the external drive causes a drawback in certain situations.
For example, such drawback occurs in a case where the image sensor chip performs a preliminary operation and a main operation, in which the main operation accesses the required image information, and the preliminary operation monitors the projection of the required image onto the image sensor chip. In such process, the main operation starts after the necessary image is projected on the image sensor chip in the preliminary operation, but the preliminary operation may continue for a long period during which the microcomputer 2 and the drive pulse generation circuit 4 have to be continuously operated, so that the consumption of the electric power continues even while the access of the required image information does not take place.